rewatching the film i caught onto this myself but i think its very deliberate on tarantinos part example when king amp django ride into daughtrey the doctor is giving the woman instructions and looks up to say its a nigger on a horse django himself repeats the line a few moments later and its funny both times i think tarantino wants us to be uncomfortable laughing at it then we warm to it throughout the movie just to be clear though the word itself isnt funny its the way its used which is likely quite deliberate